This invention relates to an improvement to fire fighting nozzles of the type disclosed in U.S. Pat. No. 4,640,461, the disclosure of such patent being hereby incorporated by reference.
The fire fighting nozzle disclosed in the '461 patent is of a type that includes a mixing nozzle and/or passage located on or proximate to the discharge port of the nozzle. More particularly, the mixing passage area is partially located between an upstream deflecting plate and a downstream mixing plate. The upstream deflecting plate forms a portion of a baffle affixed proximate the discharge end of the nozzle barrel, serving as a baffle for the flow of primary liquid through the nozzle. As shown in the embodiments of the '461 patent, the mixing plate defines a downstream wall of the mixing area or passage and typically comprises a flat plate situated perpendicular to the direction of flow of the liquid. In some embodiments, the flat mixing plate has a portion of a peripheral edge slanted upstream. In such a manner, the mixing plate deflects additive fluid outward and to some extent also backward or upstream into a stream of primary fire fighting liquid. This deflection pattern can enhance the generation of superior foam, especially when the additive fluid comprises a foam concentrate or a foam concentrate and liquid.
In some cases the energy expended in deflecting foam concentrate outward, and even upstream, in order to form a superior foam, may sacrifice too much of the total range potentially achievable by the fire fighting nozzle.
The improved mixing passage or mixing area disclosed herein, through use of novel mixing plate configurations or shapes, achieves a fortuitous compromise between the generation of superior foam and the achievement of maximum range for a nozzle. The mixing plate configurations and shapes disclosed herein deflect fluid outwardly and also partially downstream through use of at least partially outwardly conically shaped portions of the plate.